1. Field of the Invention
The present invention is generally in the field of semiconductors. More particularly, the invention relates to the packaging of semiconductor dies.
2. Background Art
An insulated-gate bipolar transistor (IGBT) can be connected to a freewheeling diode when implementing a power switch in a high power application, such as in a three-phase motor drive. In one approach to connecting the IGBT and the diode, the devices can be included in a common package, or a co-package. For example, a co-package can include the IGBT and the diode on a common substrate in close proximity. However, the IGBT and the diode may move resulting in undesirable contact and reduced reliability. For example, the IGBT and the diode may become very hot, resulting in failure of the contact to the common substrate. In another approach, the IGBT and the diode can be in separate packages to reduce the risk of movement of the IGBT and the diode. However, utilizing separate packages increases distances between the IGBT and the diode, resulting in a higher inductance connection between the devices. Furthermore, bond wires are typically employed as interconnects, resulting in reduced current carrying capability, higher inductance, and higher resistance.
In order to avoid excessive heating, a temperature sensor may monitor the temperature of the IGBT, and a heat sink may dissipate heat from the IGBT and the diode. Where the IGBT has an external temperature sensor, the temperature sensor can be difficult to place in good thermal contact with the IGBT and can also interfere with placement of the heat sink and other components. Thus, an internal temperature sensor is typically included with the IGBT. The internal temperature sensor is monolithically formed with IGBT so that the temperature sensor is in good thermal contact with the IGBT while being unobtrusive to placement of the heat sink another the other components. However, including the internal temperature sensor with the IGBT increases the size of the IGBT and, moreover, accurate measurement of the temperature signal is difficult due to a noisy environment produced by switching the IGBT. Furthermore, the internal temperature sensor requires an extra mask layer during fabrication of the IGBT, thereby increasing manufacturing cost.
Thus, it would be desirable to provide an IGBT with a diode in a higher reliability package, while avoiding the risk of the devices moving; and it would be further desirable to include a temperature sensor that does not interfere with placement of a heat sink and other components.